Why are the y values calculated in Excel not the same as those shown on the Wolfram site?
An example is given for the Wolfram site given below,
https://www.wolframalpha.com/input/?i=fourth%E2%80%90order+Runge%E2%80%90Kutta+method+%7By%27%5Bx%5D+%3D%3D+x+-+2+y%5Bx%5D%2C+y%5B1%5D+%3D%3D+2%7D+from+1.+to+1.5+stepsize+%3D+0.05&assumption=%22ClashPrefs%22+-%3E+%22%22
The Wolfram site gives y-values that differ from those I obtain on Excel (shown below),
y' = dy / dx = x -2 y yi+1 = yi + [(h) * (1/6) * (K1+2K2+2K3+K4)]
x h K1 K2 K3 K4 y exact solution 1.00 0.05 -3.000000 -2.900000 -2.902500 -2.804875 2.000000 2.000000 1.05 0.05 -2.659835 -2.568340 -2.570627 -2.481304 1.854918 1.858465 1.10 0.05 -2.352851 -2.269030 -2.271125 -2.189295 1.726425 1.732779 1.15 0.05 -2.075810 -1.998915 -2.000837 -1.925768 1.612905 1.621432 1.20 0.05 -1.825792 -1.755147 -1.756913 -1.687946 1.512896 1.523060 1.25 0.05 -1.600161 -1.535157 -1.536782 -1.473322 1.425080 1.436429 1.30 0.05 -1.396538 -1.336625 -1.338123 -1.279632 1.348269 1.360420 1.35 0.05 -1.212777 -1.157458 -1.158841 -1.104835 1.281389 1.294024 1.40 0.05 -1.046940 -0.995767 -0.997046 -0.947088 1.223470 1.236326 1.45 0.05 -0.897279 -0.849847 -0.851033 -0.804728 1.173640 1.186497 1.50 0.05 -0.762217 -0.718161 -0.719263 -0.676254 1.131108 1.143789
Do the truncations stand behind the deviations between Wolfram and Excel y-values?
Thanks.
Attachments:
